Scattered ray diaphragm



March 12, 1940. GRQSSMANN 2,193,330

* SCATTERED RAY DIAPHRAGM Filed Nov. 2, 1937 3 Sheets-Sheet 1 //7 ref?for:

/4A.AM

March 12, 1940.

G. GROSSMANN SCATTERED RAY DIAPHRAGM Filed Nov. 2, 1957 3 She ets-Sheet3 //7re/7 for:

Patented Mar. 12, 1940 UNITED STATES TENT In Germany November; l; 1936Claims. (oi. 250-42) I This invention relates to grids, used in makingradiographs, and more particularly to Bucky grids.

One of the objects of the invention is to provide for controlling thespeed of operation of a grid'from some convenient point, from aswitchboard for example, as well as actuating the said grid from saidpoint. i l

Another object of the invention is to provide =for actuating a grid froma convenient; point, a switchboard for example, and controlling orregulating the speed of operation of said diaphragm in conjunction withthe means for indicating the duration of the exposure.

Another object of the invention is to provide for actuating a grid froma convenient point, a switchboard for example, and controlling or regulating the speed of operation of said grid in conjunction with themeans for'adjusting time of the exposure. i

Another object of the invention isto provide for the selectiveoperation, from a convenient point, a switchboard for example, ofmeansfor moving the grid from one end position to the other, and ofmeansfor moving it back again.

A further object of the invention isto eliminate those speeds ofoperation of the grid which cause the production of stripe-like,shadows.

. The invention, as well as these and other objects of the invention,will be readily understood from the following description, taken inconnec tion with the accompanying drawings, of one illustrativeembodiment of the invention, the truescope of the invention beingpointed out in the appended claims.

In the drawings:

Figures 1 and 2 illustrate how the critical speeds of the grid movementare cut out.

Figure 3 shows diagrammatically illustrative step means for controllingor regulating the speed of the grid.

Figure 4 is in greater part a diagrammatic elevational of a Bucky grid,its actuating means and the means upon a switchboard for controlling orswitching said actuating means on and off.

Figure 5 shows diagrammatically the same parts as Figure 4, but in topplan View and with the electrical connections.

Among the technical operating advantages of If this speed be designatedby. 'Uk, then in the exposure, then, in addition to simplifying theoperation, the adjustment of speed of the" grid tocorrespond to the timeof exposure cannot be overlooked. Faulty exposures, such as often occurtoday either'through neglect to regulate or adjustthe speed of the gridor to adjust said speed in accordance with the time of exposure,

are thusavoided.

Films made; with a Bucky grid, often show band-like shadows. Thecontrast between said shadows and the exposed portions between them 20oftenvaries in different exposures. It is often, so great that the'valueof the film is greatly diminished. Such' band-shadows. always occur,

,Wl'ljel'lthe projection of theshadows made by the gridelementscoincides with the high spots of the X-ray tube voltage. l

To avoid such; shadows, it has, been proposed to vary the size of thespaces between grid elementslengthwise of the grid. Such grids, however,are suited to making exposures only under special conditions, andstillless to radioscopy, as the variation in the grid spacinginjuriously afroots the radioscopic picture.

The present invention overcomes this difficulty by so regulating oradjusting the speed of the grid,that all speeds which give rise to suchband shadows, are eliminated. Such speeds are herein called. criticalspeeds. l

I have found that such band-shadows occur 4 most strongly, whenthe timeperiod required for the grid "toimove through a distance d equal to halfthe space between two consecutive grid elements, equalsthe phasediiference t of two successive peaks of the X-ray tube voltage, that isto say when the grid speed equals case of a half wave apparatus, t=T; Tbeing the period or cycle of the alternating or rotary current foroperating the X-ray apparatus in the case of a full-valve rectifyingapparatus NIH and in the case of a 3-phase full-wave rectifyingapparatus Band-shadows oi the first category occur, when the speed V ofthe grid equals ibetc.

in general is equalto m being a whole number. As m increases, the

contrast between the band-shadows and the most exposed portions of thefilm decreases. When band-shadows of the third category occur. etc. Theappearance of the band-shadows formation, is so selective, that a smallvariation inythe grid speed from any one of the critical 7 speedswillsuflce to produce a picture free from band shadows.

In order that always the same number of grid elements shall pass overany point of the film during the exposure, whatever may be the time ofexposure used, the speed '0 of the grid will be so adjusted or regulatedthat it shall be inversely proportional to the time of exposure Z, andshall vary with thetime of exposure Z as indicated by the parabola inFig. 1. In said figure grid speeds 0, v1 and 112 corresponding to thetimes of exposure 0.5,-1.0 and 2.08, designate critical speeds of thegrid diaphragm.

In accordance with the present invention, in

order to prevent the grid from moving at the critical speed on or 121 or112 when the device is adjusted for a time of exposure 0.5 or 1 or 2c,the increase of resistance of the step by step reguiator, whichregulates or adjusts the speed of the grid will be discontinuouslyvariable for each unit of length of the circumference'in such mannerthat the broken curve shown in Fig. 2 shall represent the grid speed independence on the time of exposure Z. The arrangement will be such thatthe grid speed shall remain unchanged and equal "to v1.1 within therange of Z=1.1s to about Z:0.85s (v1.1 indicating the speedcorresponding to Z=1.1 according to Fig. 1) and on the passage fromZ=0.85s to Z=0.8s, suddenly rises to the ordinate value v0.8corresponding to the curve in Fig. 1. This discontinuous spot willpreierably'be given a Z-value which shall lie between two scaledivisions of the time lag relay.

In practice this is accomplished by short-circuiting the contact studsK9, K10, K11 carried by a suitable mounting of insulating material (notshown) on the speed regulator for the grid (see Fig. 3) corresponding toscale divisions 0.9-5, 1.0s

and .1 .1s.of the step regulator for regulating the grid speed, andthrowing in a resistance R, corresponding to the entire speed difference00.8-01.1 (see Fig. 1) between the contact studs K8 and K9 correspondingto the scale divisions 0.8s and 0.9.9 of the time lag relay. Saidresistance R is a multiple of the resistances 1, 1" which are between K7and K8 or K11 and K12 respectively. The same procedure is adopted inrespect to the points of the regulating resistance to which correspondthe critical grid speeds v0, 212 etc.

In Figures 4 and 5 is shown an illustrative embodiment of the inventioncomprising a Bucky grid moved as described, controlled from a distanceand the speed of operation of which is positively regulated or adjusted,as well as the switches and connection for its operation. In saidfigures said grid is in starting position which it occupies beforebeginning an exposure; the X- ray apparatus is switched off ordisconnected, all the switches on the switchboard are in oli positionand the time lag relay or exposure timing means is adjusted for thedesired time of exposure.

In said illustrative embodiment of the invention, a Bucky grid I (seeFig. 4) is provided with guide rolls 2 which run upon guide rails 3,said grid being conveniently driven by a motor 4, a series motor orthree phase motor, for example, of any suitable convential construction.Said motor drives said grid through suitable driving connection, hereina driving gear 5, 6 and endless belt 8. Normally said grid isdisconnected from said driving gear, means being provided to connect itthereto when desired. Any suitable means may be provided for thatpurpose without departing from the scope of the invention. Herein saidmeans comprising conveniently two electromagnets 9, II], II and I9, 20,2|, one of which serves to move said grid in one direction, the other inthe other direction. Means as hereinafter more fully described areprovided for energizing said magnets from any suitable source ofelectrical energy, such as line wires 40, 41.

Magnet core 9 is carried by said grid upon one side of the upper sectionof said belt, the vertically movable armature ll of said magnet beinglocated uponthe opposite side of said belt-section. The belt is drivenby said motor in the direction indicated by the arrows in Figure 4, sothat when said magnet 9, H), I l is energized, said belt will be clampedbetween said core and said armature and said grid will be moved from itsposition of rest from left to right, (Fig. 4) during the exposure. Aspring l2 tends to return said armature to its inoperative position whensaid magnet is de energized. To return said grid from right to left(Fig. 4) to its starting position after the exposure is terminated,magnet 19, 20, 2| will be energized to cause its armature 2|, situatedupon one side of the lower section of said belt to clamp the latterbetween it and the magnet core 19 of said magnet, carried by said gridupon the other side of said belt section. A spring 22 tends to move saidarmature 2i away from its core 19 to unclamp said belt, when said magnetis deenergized.

Means are provided for regulating or adjusting the speed of the motor 4and hence the speed of the grid 1. Within the scope of the invention anysuitable means may be provided for this purpose, said means hereinconveniently comprising a regulating resistance herein convenientlymounted upon the switchboard 50 and illustratively' constructed as shownin Figures 3 and 4. It comprises a regulating or adjusting lever 8|which is connected to the adjusting lever 6| of 2,199,350 the time lagrelay 60. In the drawings said lever 6| ofsaid relay is set on the scaledivision 82. (See Fig. 5.) A lever 63 is controlled by the relaymechanism when the latter runs down, to open contact 64, t5 and thusswitch off or disconnect the X-ray apparatus.

A switch 52 is connected to the shaft 5| of the operating switch of theX-ray apparatus. In the drawing said switch 52 is shown in its offposition 53. Position 55 is the on position for operation of theapparatus to make an exposure.

Before starting an exposure, the operating switch is moved to the on oroperating position,

whereby switch 52 will be moved to position 55 i This closes the circuitof motor 4 and (Fig. 4). of its regulating resistance 80, thus startingsaid motor and setting said belt 8 in motion. make the exposure, a pushbutton switch 66 on the switchboard 50 is closed, thus connectingwinding ill of electro-magnet 9, ill, H to the line wires 49, ll throughwinding-68 of an electromagnet 68, 69. Armature 69 of said magnet isthus operated tosho rt-circuit the contact of press button switch 66, sothat circuit of magnet winding ill will remain closed even though saidpress button switch 65 be pressed only momentarily. Electro-magnet 9,it, H clutches the gridto the travelling endless belt 8, thus settingsaid grid in motion. Shortly after said grid starts its movement, railcontact 36, carried by said grid, shortcircuits contacts 3!, 32, andconnects conductors 33, 34, magnet35, 36 which serves to short-circuitthem, and winding 90, which controls the closing of switch 90, ill, toline wires 40, 4|, through closed switch ll. Switch SI of the X-rayapparatus is thus closed and primary 93 of the X-ray transformer orofthe step transformer which serves to regulate the same, is connectedtosaid line wires ill, ii.

Upon expiration of the time of exposure for which said time lag relayfill is adjusted, lever 63, actuated by said relay, meets contact .65,separates it from contact 66 and thus breaks the supply circuit ofelectro-magnet winding 90, thus switching off the X-ray apparatus.Shortly thereafter, lever l5, carried by said grid I, meets contactlever H, separates it from contact l6, and thus breaks the supplycircuit of said magnet winding ill, which results in making the magnetconnection between said grid l and said travelling belt 8, and arreststhe movement of said grid.

After making the exposure, said operating switch will be thrown into itsoff position, whereby contact lever 52 will be brought into position 53.In order to return said grid to its initial or starting position aftermaking an exposure, switch 52 will be moved to position 54, wherebymotor 4, which was cut out meanwhile, is again set in operation. Pressbutton switch 76 Will also be closed, thus connecting winding 28] ofelectromagnet i9, 20, 2! to line wires 40, 4!, magnet i9, 20, 2! beingthus energized, clutches said grid to the lower section of saidtravelling belt 8 (Fig. 4). As the grid I reaches its initial startingposition,

lever l5 breaks the contacts 26, 21, and therefore of magnet winding 90.This is to prevent the X- ray apparatus from being switched on at themoment when in the return movement of said grid to its startingposition, the rail-contact carried by said grid, glides over contacts3|, 32.

By the above arrangement for the first time adjustment of the speed ofmotion of the grid in dependence upon the selected time of exposure, andthe return of said grid to its initial or starting position, from aswitchboard, or other convenient point, is made possible. By thecorresponding suitable construction of the controlling or regulatingresistance 83, the occurrence of interfering band-shadows, on thefilnipicture is prevented, as previously set forth.

Press button switch i6 could be replaced by a switch, operable, forexample, by said automatic adjusting lever ill of said time lag relay.It is preferable, however, that said levers 6! and 8!, be connected asabove described in the illustrative embodiment of the invention hereinshown, as this enables the time of exposure and speed of operation to beadjusted by a single handle.

if, instead of a time lag relay, a relay be used which cuts out theX-ray apparatus so soon as definite quantity of current has been appliedto the X-ray tube, I provide suitable means, actuatedby the adjustingmeans of said last named relay, and which indicates the time ofexposure.

In such case the means for regulating or adjusting the speed of the gridwill, in accordance with the present invention, be connected to themeans for indicating the time of exposure, that isto say the means forindicating the time of exposure will replace the time lag relay of Figs.4 and 5; in that case 6! would designate a hand actuated by the meansfor adjusting the quantity of current supplied to the X-ray tube, andwhich indicates the time of exposure upon a time scale, while lever 63would designate a lever actuated by the operation of the relay whichcontrols the quantity of current supplied to the X-ray tube.

I am aware that the invention may be embodied in other specific formswithout departing from the spirit or essential attributes thereof, and Iillustrative and not restrictive, reference being had to the appendedclaims rather than to the foregoing description to indicate the scope ofthe invention.

I claim:

1. In X-ray apparatus the combination of a movable, electrically drivenBucky grid for X-ray radiography; means for setting the period ofexposure; and controlling means for regulating the speed of movement ofsaid grid, said controlling means being coupled with said means forsetting the period of exposure, whereby setting the period of exposurewill automatically adjust the speed of the grid to correspond to theperiod of exposure.

2. In X-ray apparatus the combination of a movable, electrically drivenBucky grid for X-ray radiography; means for indicating the period ofexposure; and controlling means for regulating the speed of movementofsaid grid, said controlling means being coupled with said indicatingmeans, whereby operation of the latter will automatically adjust thespeed of the grid to correspond thereto.

3. The combination of a power driven endless belt; a Bucky grid forX-rayradiography; two electromagnetic clamping means connected to said grid;and controlling means selectively operable to cause one of said clampingmeans to clamp said grid to that part of said belt moving in onedirection and the other of said clamping means to clamp said grid to apart of said belt moving in the opposite direction.

4. In X-ray apparatus, the combination of a movable, electrically drivenBucky grid; means for setting the milliamperage to be supplied by saidapparatus; means for setting the milliampere-seconds to be delivered bysaid apparatus for a radiograph; and controlling means for regulatingthe speed of said grid, said controlling means being coupled with saidX-ray milliamperage setting means, whereby setting the milliamperagewill automatically adjust the speed of the grid to correspond.

5. In X-ray apparatus, the combination of a movable, electrically drivenBucky grid; means for setting the milliamperage to be suppied by saidapparatus; means for setting the milliampere-seconds to be delivered bysaid apparatus foran X-ray radiograph; and controlling means forregulating the speed of said grid, said controlling means being coupledwith said means for setting the milliampere-seconds whereby setting thelatter will automatically adjust the speed of the grid to correspond.

6. The combination of an electrically driven Bucky grid for X-rayradiography; means for regulating the speed of movement of said grid;and a scale for adjusting said regulating means,

the graduations of said scale corresponding to such speeds only of saidgrid as will not produce shadows upon the radiograph.

7. In X-ray apparatus, the combination of an electrically driven Buckygrid movable in the same direction during the exposure period; drivingmeans for moving said grid in opposite directions, said driving meansbeing normally inoperative to move said grid; and means to render saiddriving means operable alternatively to move said grid in one or theother direction.

8. In X-ray apparatus, the combination of an electrically driven Buckygrid movable in the same direction during the exposure period; drivingmeans adapted to move said grid in opposite directions, said drivingmeans being normally inoperative to move said grid; mechanism adaptedoperatively to connect said driving means to said grid; and means toactuate said mechanism operative to connect said driving means to saidgrid alternatively to move said grid in one or the other direction.

9. In X-ray apparatus, the combination of an electrically driven Buckygrid for X-ray radiography; a multi-contact resistance regulator forregulating the speed of movement of said grid; and means to variablyadjust said regulator to drive said grid at such speeds only as will notproduce band shadows on the radiograph.

10. The combination of an electrically driven Bucky grid, movable in thesame direction during the exposure period; and two electric devicesselectively controlled, the one to move said grid from starting positionto its opposite terminal position in one direction, and the other tomove said grid from said terminal position back to its startingposition.

GUSTAV GROSSMANN.

